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2010 Ford Mustang - Battery issue?

Been getting a battery warning light for almost a week. had battery AND alternator checked by autozone, oreillys and ford house. All three said alternator was good, but ford house said battry failed whatever test they did. Replaced battery today, not only is battery light still on, dashboard, radio and AC went out on the ride home, except for the stupid battery light. Would try to kick back on a few times but would cut out again. I figure this is wiring more than anything else. Thoughts???

So hat are you calling a “Ford House?” The dealer? Or another parts store?

What voltage are you seeing while the engine is running? And is the check engine light on? Or only the battery light?

The powertrain control module controls the alternator output under all conditions. It reads the voltage and tell the alternator to charge normally, more or less. All of these inputs and outputs can be monitored with a scan tool. All Ford dealers have this tool, as well as other places.

Given you’ve changed the battery, the light is still on, I’d say the voltage regulator in the alternator has failed. Easy to check on the car. Maybe you should find a real mechanic rather than auto parts stores.